Water-resistant additives for gypsum wood fiber products

ABSTRACT

Emulsion are provided which are useful in imparting water resistance to gypsum products. In one embodiment, the emulsion comprise a plurality of waxes, at least one saponified wax, a complexed starch, a polymerized alkyl phenol, and a small amount of a co-surfactant. In another embodiment, the emulsion comprise a single wax, a balanced dual surfactant system, a complexed starch and a polymerized alkyl phenol. Emulsion of this embodiment may be added to hot, even boiling, water without the emulsion separating or curdling. The emulsion of the present invention are stable for extended periods of time when stored at room temperature and do not require the addition of a bactericide. The emulsion of the present invention are pourable liquids at room temperature.

This application claims the benefit of U.S. Provisional Application No.60/435,329, filed 20 Dec. 2002, and U.S. Provisional Application No.60/454,131, filed 12 Mar. 2003.

FIELD OF THE INVENTION

The present invention relates to an additive useful in improving thewater-resistance of gypsum wood fiber products. The present inventionalso relates to an emulsion which includes a wax or a combination ofwaxes, an alkyl phenol, at least one surfactant, polynaphthalenesulfonicacid, and an alkali metal hydroxide, the emulsion useful in improvingthe water resistance of gypsum wood fiber products. The presentinvention further relates to a method of malting the emulsion.

BACKGROUND OF THE INVENTION

Certain properties of gypsum (calcium sulfate dihydrate) make it verypopular for use in making industrial and building products; especiallygypsum board. It is a plentiful and generally inexpensive raw materialwhich, through a process of dehydration and rehydration, can be cast,molded or otherwise formed to useful shapes. The base material fromwhich gypsum board is manufactured is the hemihydrate form of calciumsulfate (gypsum), commonly termed stucco, which is produced by the heatconversion of the dihydrate from which the water phase has been removed.

In the making of gypsum board, the gypsum slurry must flow onto a papersubstrate. In a continuous process, the slurry/substrate combination isthen sized by passing this combination between rollers. Simultaneouswith this sizing step, a paper backing is positioned over the sizedgypsum slurry. Accordingly, the gypsum slurry must possess sufficientfluidity so that a properly sized gypsum board can be made.

It is also important to the manufacture of gypsum board, that the gypsumslurry be capable of being foamed to a limited extent. Foamabilityrefers to this ability to be foamed. When the gypsum slurry and papersubstrate are passed through the sizing rollers, a certain amount of thegypsum slurry must back flow and accumulate in the rollers nip so that asteady flow of gypsum is delivered to the sizing rollers.

Because of the continuous nature of a gypsum board manufacturing processwherein the gypsum slurry flows onto a substrate which then passesthrough sizing rollers, the extent to which the gypsum slurry flowsafter it is sized is critical to maintaining the finished productdimensions of the gypsum board. The time at which the gypsum slurryceases its flow is referred to as the pre-set time. The set time of thegypsum slurry is also an important property. The set time refers to theamount of time it takes the gypsum slurry to be dried, under heat, tothe finished, solid gypsum board.

Gypsum board absorbs water, which reduces the strength of the wallboard.Prior art products, like ordinary gypsum board, gypsum tile, gypsumblock, gypsum casts, and the like have relatively little resistance towater. When ordinary gypsum board, for example, is immersed in water,the board quickly absorbs a considerable amount of water, and loses agreat deal of its strength. Actual tests have demonstrated that when a 2inch by 4 inch cylinder of gypsum board core material was immersed inwater at about 70° F., the cylinder showed a water absorption of 36%after immersion for 40 minutes.

The gypsum wood fiber (GWF) product differs from conventional gypsumwallboard products in that the GWF incorporates into the establishedslurry both gypsum and wood fibers. For example, in addition to lumber,particleboard, fiberboard, waferboard, plywood, recycled pulp and paper,and “hard” board (high density fiberboard) are some of the forms ofprocessed lignocellulosic material products used in the buildingindustry. Such materials have better tensile and flexural strength thangypsum. However, they are also generally higher in cost, have poor fireresistance and are frequently susceptible to swelling or warping whenexposed to moisture. Therefore, affordable means to improve upon theseuse limiting properties of building products made from cellulosicmaterial are desired.

Previous attempts to combine the favorable properties of gypsum andcellulosic fibers, particularly wood fibers, have had very limitedsuccess. Attempts to add cellulosic fibers, (or other fibers for thatmatter), to gypsum plaster and/or plasterboard core have generallyproduced little or no strength enhancement because of the heretoforeinability to achieve any significant bond between the fibers and thegypsum. U.S. Pat. Nos. 4,328,178; 4,239,716; 4,392,896 and 4,645,548disclose recent examples where wood fibers or other natural fibers weremixed into a stucco (calcium sulfate hemihydrate) slurry to serve asreinforcers for a rehydrated gypsum board or the like.

U.S. Pat. No. 4,734,163, teaches a process in which raw or uncalcinedgypsum is finely ground and wet mixed with 5-10% paper pulp. The mash ispartially dewatered, formed into a cake and further dewatered bypressure rolls until the water/solids ratio is less than 0.4. The cakeis cut into green boards, which, after being trimmed and cut, arestacked between double steel plates and put into an autoclave. Thetemperature in the autoclave is raised to about 140° C. to convert thegypsum to calcium sulfate alpha hemihydrate. During the subsequentincremental cooling of the vessel boards, the hemihydrate rehydratesback to dihydrate (gypsum) and gives the boards integrity. The boardsare then dried and finished as necessary.

U.S. Pat. No. 5,320,677 to Baig describes a composite material made fromgypsum and host particles of a reinforcing material, such aslignocellulose fibers. The composite material is produced by mixinggypsum and host particles of a stronger substance, such as wood fibers,in a dilute aqueous slurry. The slurry is heated in an autoclave,preferably under pressure, to convert the gypsum to calcium sulfatealpha hemihydrate. The hot, converted slurry is discharged through aheadbox onto a continuous felting conveyor of the type used in papermaking operations, where the slurry is dewatered to remove as muchuncombined water as possible before rehydrating the hemihydrate back togypsum. The resulting material is a homogeneous mass comprising gypsumcrystals physically interlocked with the discrete host particles. Theresulting mat is then dried in heated convection or forced air dryingovens, and the dried board is cut to the desired dimensions. Baigteaches the addition of crystal modifiers to the slurry, but does notteach the addition of any additive to improve the water resistance ofthe final product.

These prior art products, like ordinary gypsum wallboard, gypsum tile,gypsum block, gypsum casts, and the like have relatively littleresistance to water.

U.S. Pat. No. 6,010,596 to Song teaches adding a wax emulsion containinga combination of a paraffinic hydrocarbon, montan wax, polyvinylalcohol, water and emulsifiers to a hot slurry containing ground gypsumand wood fiber. Emulsifiers include nonionic and cationic surfactants.While still hot, the slurry is discharged through a headbox onto acontinuous felting conveyor, such as the type used in paper makingoperations, to form a felter cake and remove as much uncombined water aspossible. Song does not teach an emulsion containing the novelcombination of waxes, an alkyl phenol, at least one surfactant,polynaphthalenesulfonic acid, and an alkali metal hydroxide.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide an additive emulsion and amethod for malting the emulsion that addresses the issues of waterabsorption, viscosity control, stability, and slurry fluidity in themanufacture of gypsum wood fiber composites.

In one embodiment, the present invention provides an emulsion includingat least one wax, an alkyl phenol, at least one surfactant, apolynaphthalenesulfonic acid, an alkali metal hydroxide, and water. Thepolynaphthalenesulfonic acid and the alkali metal hydroxide react togive a salt of polynaphthalenesulfonic acid. Emulsions of thisembodiment may be added to hot, even boiling, water without the emulsionseparating or curdling. At room temperature, the emulsions of thepresent invention are pourable liquids and are stable for extendedperiods of time. The emulsions of the present invention, when addedduring the manufacture of gypsum wood fiber composites, improve thewater-resistance of the composite.

In another embodiment, the present invention provides an emulsionincluding at least one wax, an alkyl phenol, at least one surfactant, apolynaphthalenesulfonic acid, an alkali metal hydroxide, water, and astarch.

In another embodiment, the present invention provides an emulsionincluding at least one wax, an alkyl phenol, at least one surfactant, apolynaphthalenesulfonic acid, an alkali metal hydroxide, water, and acomplexed starch.

In another embodiment, the present invention provides a method formaking an emulsion, including the steps of:

-   -   (a) heating to a temperature ranging from about 185° F. to about        210° F. a mixture containing at least one wax, an alkyl phenol,        and at least one surfactant to provide a wax phase mixture;    -   (b) heating to a temperature ranging from about 185° F. to about        210° F. a mixture containing polynaphthalenesulfonic acid, an        alkali metal hydroxide, and water, to provide a water phase        mixture;    -   (c) adding the water phase mixture to the wax phase mixture to        provide a mixture;    -   (d) homogenizing the mixture of step (c); and    -   (e) cooling the homogenized mixture at a rate effective to        control the stability and viscosity of the homogenized mixture.

Another embodiment of the invention is directed to a gypsum wood fibercomposite manufactured using the emulsion of the present invention and aconventional paper malting process.

A further embodiment of the present invention is an emulsion containinga first wax having a melting point of at least 120° F. in an amount ofabout 30 wt. % to about 45 wt. % by weight, based on the total weight ofthe emulsion; a saponifiable wax in an amount from about 3 to about 5wt. %, based on the total weight of the emulsion; a combination ofsurfactants in an amount from about of about 0.5 to about 5 wt. %, basedon the total weight of the emulsion; an alkyl phenol in an amount fromabout of about 0.5 to about 10 wt. %, based on the total weight of theemulsion; a polynaphthalenesulfonic acid in an amount from about 0.25%to about 5 wt. %, based on the total weight of the emulsion; water in anamount from about 45 to about 65 wt. %, based on the total weight of theemulsion; and an alkali metal hydroxide in an amount from about 0.5% toabout 3 wt. %, based on the total weight of the emulsion.

DETAILED DESCRIPTION OF THE INVENTION

The Gypsum Wood Fiber (abbreviated as “GWF”) product differs fromconventional gypsum wallboard products in that the GWF incorporates intothe established slurry both gypsum and wood fibers in a uniquecombination and ratio of from about 5 to 50 parts of wood fiber to acorresponding quantity of gypsum to achieve a 100% combination in amixed form. Unlike the production of gypsum wallboard which incorporatesa slurry through a formation mechanism and which requires that anyadditives tributary to the slurry chemistry not affect the fluidity ofthe slurry during the manufacturing process but control the inherentformation of process foam, the production of GWF is facilitated througha conventional paper making process utilizing a wet end section headboxdistribution mechanism distributing the GWF slurry onto a vacuum wirefor initial mat formation and dehydration followed by compressionthrough a series of vacuum belt rolls and into a kiln for finaldehydration. The addition of the emulsion must not cause wax plating orbreakout on the vacuum belt. The GWF of the present invention does notincorporate paper face and back paper but rather is a paperless corethat has similar performance and uses comparable to conventionalsheathing products currently available.

The unique combination and ratios thereof of a C₂₄-C₃₆ and greaterpolymerized alkyl phenol, various waxes, co-surfactants selected fromsorbitan esters such as fatty acid esters hexaoleate, polyoxyethylenesorbitan fatty acid esters, and a salt of polynaphalenesulfonic acidresults in a stable wax emulsion suitable for incorporation into a GWFcomposite.

A preferred formulation is as follows in Table 1: TABLE 1 Raw MaterialIngredient Weight % 145° F. Melt Point Wax 37.9 Saponifiable Wax 5.0C₂₄-C₃₄ Alkyl Phenol 5.0 SPAN 60 0.3 TWEEN 60 1.7 45.5% KOH 0.1Polynaphthalene sulfonic acid 1.0 Water 49.0

The process of water felting dilute aqueous dispersions of variousfibrous materials is a well-known commercial process for manufacturingmany types of paper and board products. In this process, an aqueousdispersion of fiber, binder and other ingredients, as desired ornecessary, is flowed onto a moving foraminous support wire, such as thatof a Fourdrinier or Oliver mat forming machine, for dewatering. Thedispersion may be first dewatered by gravity and then dewatered byvacuum suction means; the wet mat is then pressed to a specifiedthickness between rolls and the support wire to remove additional water.The pressed mat is then dried in heated convection or forced air dryingovens, and the dried material is cut to the desired dimensions.

An embodiment of the invention is further directed to a method formaking a gypsum wood fiber article, which includes the steps of:

-   -   (a) mixing a slurry containing from about 5 wt. % to about 50        wt. % of a wood fiber, from about 5 wt. % to about 50 wt. % of        gypsum, from about 1 wt. % to about 3 wt. % of the emulsion of        the present invention, based on the total weight of the slurry        and water;    -   (b) distributing the slurry onto a vacuum wire for formation of        a mat;    -   (c) partially drying the mat of step (b);    -   (d) compressing the mat of step (c) through a series of vacuum        belt rolls; and    -   (e) drying the compressed mat of step (d) in an oven.

The amount of water in the slurry is an amount sufficient to distributethe slurry onto a vacuum wire for the formation of a mat. Various gypsumwood fiber articles may be made by this method including, but notlimited to, wallboard and sheathing.

It has also been discovered that by utilizing starch compounds such asacid-modified, hydroxyethylated, oxidized, and/or cationic, incombination with a complexing agent and a salt ofpolynaphthalenesulfonic acid coupled with a polymerized alkyl phenol allin a correct relationship, that the noted deficiencies are corrected anda resulting wax emulsion having superior performance as a waterabsorption control additive is achieved. Furthermore, the compositionsof the present invention function as anti-build-up additives withrespect to wax build-up on the vacuum belt.

It has further been discovered that borate compounds, molybdatecompounds, and molybdenum compounds are surprisingly effectivecomplexing agents. Hereinafter, generically, molybdate and molybdenumcompounds of the present invention will be referred to as molybdenumcompounds. Examples of useful complexing agents include, but are notlimited to, sodium borate, magnesium borate, and other borate compounds;ammonium molybdate, sodium molybdate, magnesium molybdate, and othermolybdate compounds; molybdenum disulfide and other molybdenumcompounds.

The ratio of complexing agent (for example, sodium tetraboratedecahydrate, sodium molybdate dihydrate, molybdenum disulfide, or othercompounds) to the modified starch significantly influences the controlof other necessary properties in the board/slurry process, i.e. foamsupport and slurry additive compatibility.

It has further been discovered that these combinations and the ratiosthereof are unique and necessary to formulate a stable and performingwax emulsion and that certain manufacturing processes must occur. Therange of ratios of starch:borate, or starch: molybdenum compound mayrange from about 4:1 to about 20:1 on a weight/weight basis.

A further embodiment of the invention is directed to a gypsum wood fiberarticle containing wood fiber, gypsum and the wax emulsion of thepresent invention.

In the manufacture of gypsum wood fiber wallboard products it isimportant to impart water-resistance to the finished product, so as tolimit the maximum water absorption realized by the wallboard in adefined board soak test. For example, American Standards for TestingMaterials ASTM 1396 and sub parts thereof describe such a test.

Preparation of Emulsions:

In one embodiment of the present invention, water, a complexing agent(that is, a borate compound, or a molybdenum compound) and a starch arefirst brought together in order to make the complexed starch useful inembodiments of the present invention. Next, polynaphthalenesulfonic acidand potassium hydroxide are added to the aqueous solution of complexedstarch. This mixture is brought to a temperature of about 185° F. toabout 205° F. and held until the starch reaches its maximum state ofgelation, which typically occurs in about 20 to about 30 minutes. Thewax compounds are incorporated with the polymerized alkyl phenol andbrought to a temperature of about 185° F. to about 205° F. Then, the waxphase is added to the water phase and reacted to form an in situsufactant. A detergent/dispersant is formed by the combination andreaction of the polymerized alkyl phenol and the polynaphthalenesulfonicacid, which acts to modify the wax crystal and allows the wax crystalsto resist plating and linking with themselves and instead remain in adisassociated state until they are transferred due to polarity to thegypsum. The reacted system is then passed through a homogenizer at apressure of about 2,000 to about 4,000 psi and then cooled at aprescribed rate to control the stability and viscosity of the finishedwax emulsion. The homogenized composition exits the homogenizer at atemperature of about 135° F. to about 145° F. The mixture is then cooledto about 80° F. to about 110° F. The cooling rate is controlled to avoidcausing the wax to recrystallize and breakout of solution.

The term “wax emulsion”, as used herein, means an aqueous emulsion ofone or more waxes which is emulsified through the use of one or moresurfactants. The wax emulsion must comprise a wax or waxes adapted toprovide water resistance to the finished product. The wax or waxes mustbe inert with respect to the gypsum and wood fibers which make up theproduct.

Emulsions are prepared by heating the wax, an alkyl phenol, and at leastone surfactant (“wax phase mixture”) in one vessel and the water,polynaphthalenesulfonic acid, an alkali metal hydroxide (“water phasemixture”) in another vessel. Both mixtures were heated, with mixing, toa temperature from about 185° F. to about 210° F. Next, the watermixture was poured into the wax mixture under mixing. The resultantmixture was then placed in a homogenizer. With homogenization it ispreferred that a distribution of micelle diameters ranging from about0.6 micron to about 1.8 micron be achieved. However, the distribution ofmicelle diameters may range from about 0.5 micron to about 2.5 micron.This level of homogenization may be attained, for example, by using adual orifice homogenizer operating at from about 2,000 to about 4,000psig., preferably from about 2500 to about 3000 psig.

The homogenized mixture is cooled after the homogenization step at arate effective to control the stability and viscosity of the homogenizedmixture. The viscosity of the homogenized mixture ranges from about 30to about 200 cps., preferably from about 80 to about 100 cps. It is mostpreferable that the homogenized mixture be cooled from approximately185° F. to about 100° F. This may be accomplished by running thehomogenized mixture though a cooling coil immersed in water maintainedat room temperature.

HLB Values:

The hydrophilic/lipophilic balance (“HLB”) value describes therelationship of a compound to its solubility in water. An emulsifierhaving a low HLB value will tend to be oil soluble and one having a highHLB value will tend to be water soluble. Typically, a water solubleemulsifier or blends thereof are used to make an oil/water emulsiontypical of those described herein, or to solubilize oils or waxes, or toobtain some measure of detergent action. Thus, the HLB value can be usedto describe or select the proper emulsifier or emulsifier system.

Where two or more components are combined, the HLB value of thecombination is the weighted average of the individual HLB values. Thefollowing formula may be used to calculate the HLB value of acombination of materials:${{{HLB}\quad({combined})} = \frac{{Q_{1} \times ( {HLB}_{1} )} + {Q_{2} \times ( {HLB}_{2} )} + {\ldots\quad Q_{n} \times ( {HLB}_{n} )}}{Q_{1} + Q_{2} + {\ldots\quad Q_{n}}}};$

-   -   where,        -   Q₁=weight of material 1; HLB₁=HLB value of material 1        -   Q₂=weight of material 2; HLB₂=HLB value of material 2        -   Q_(n)=weight of material n; HLB_(n)=HLB value of material n            Water Absorption Test:

The affect on water absorption of the compositions of the presentinvention was determined using the following procedure:

1) Make paper pulp: Blend 3.2 grams paper with 200 g H₂O in blender seton low speed for 2 minutes.

2) Stir and heat pulp on hot plate until mixture reaches 190° F., thenadd 31.8 grams B-Base stucco and stir constantly until 190° F. usachieved.

3) On hot plate and stirring mixture, add 0.32 grams of a heat resistantadditive (“HRA”), such as calcined gypsum, and 0.067 g papermakers alum.Remove from hot plate and add calculated amount of a water resistantemulsion of the present invention (“WR”) using disposable pipette. Thecalculation is: 1/× grams WR where X is the solids content of theemulsion. For example; if the solids content is 40% add 1/0.4=2.5 gramsemulsion to the hot mixture. This approximates a typical 3% WR usagelevel in line production. Place mixture on hot plate, stir and holdtemperature for 1 minute.

4) Vacuum-filter the pulp/slurry mixture to produce even filter cake.Using the equipment described above this should take approximately 30seconds. Remove the filtered cake to an aluminum pan and peel filterpaper. Allow the cake to set for 20 minutes at ambient temperature, thenplaced in 180° F. oven for 30 minutes, then dry to constant weight at100° F.

5) Weigh the dried cake. Immerse the cake in water for 30 minutes. Blotout excess water and weigh the cake again. Calculate water absorption.

Materials:

Various sources of gypsum may be used in the compositions of the presentinvention. The term “gypsum”, as used herein, means calcium sulfate inthe stable dihydrate state; i.e., CaSO₄2H₂O, and includes the naturallyoccurring mineral, the synthetically derived equivalents, and thedihydrate material formed by the hydration of calcium sulfatehemihydrate (stucco) or anhydrite. The term “calcium sulfate material”,as used herein, means calcium sulfate in any of its forms, namelycalcium sulfate anhydrite, calcium sulfate hemihydrate, calcium sulfatedihydrate and mixtures thereof. Gypsum is available from mostcoal-burning power plants such as Duke Power or Kentucky Power.

The term “gypsum wood fiber” (GWF), as used herein, is meant to cover amixture of gypsum and host particles, e.g, wood fibers. However, theamount of water required to hydrate a gypsum sample will vary with thepurity of the sample. The amount of gypsum present in the mixture rangesfrom about 5 parts to about 50 parts, based on the total weight of themixture. The wood fiber is commonly referred to in the art as woodfurnish. Examples of wood fiber include, but are not limited to,softwood sources such as pines, spruces and firs, and hardwood sourcessuch as oaks, maples, eucalyptuses, poplars, beeches, and aspens.

Waxes useful in making the various embodiments of the present inventionmay be selected from any of the commercially known waxes which have amelting point of from about 120° F. to about 150°, and preferably fromabout 135° F. to about 145°. Such waxes are typically of low volatility,exhibiting less than about a 10% loss in weight during standardthermogravimetric analysis. Also, the oil content of these waxes istypically less than about 1% by weight. These waxes are of a relativelyhigh molecular weight, having an average chain length of C₃₆, that is a36 carbon chain length, or greater. A preferred wax is Honeywell 3816.The wax is present in an amount ranging from about 30 to about 45 wt. %,based on the total weight of the emulsion.

A preferred combination of waxes is a combination of montan wax andHoneywell 3816. In this preferred embodiment, the amount of montan waxpresent ranges from about 3 to about 5 wt. % and the amount of Honeywell3816 present ranges from about 30 to about 45 wt. %, based on the totalweight of the emulsion.

In certain embodiments, it is useful to saponify one or more of thewaxes. In this way, the saponified wax functions as an added surfactant.Waxes useful in this respect are limited to waxes having an acid valueor a saponification value and a melting point greater than about 180° F.Saponification of such waxes may be accomplished by combining the waxwith a strongly basic material such as sodium hydroxide or potassiumhydroxide. Waxes which may be saponified in the emulsions of the presentinvention include montan wax, carnauba wax, beeswax, bayberry-myrtlewax, candelilla wax, caranday wax, castor bean wax, esparto grass wax,Japan wax, ouricury wax, retamo-ceri mimbi wax, shellac, spermaceti wax,sugar cane wax, wool-lanolin wax, and others. The amount of stronglybasic material needed to saponify a wax may be calculated based on thesaponification value of the wax. For example, the saponification valuedivided by 1000 equals the grams of potassium hydroxide to add per gramof wax.

The alkali metal hydroxide is selected from the group consisting ofsodium hydroxide and potassium hydroxide. The amount of alkali metalhydroxide present in the emulsion ranges from about 0.5 to about 3.0 wt.%, based on the total weight of the emulsion.

Surfactants include, but are not limited to sorbitan esters. Examples ofsuitable sorbitan esters include, but are not limited to, sorbitan fattyacid esters, fatty acid esters hexaoleate, polyoxyethylene sorbitanfatty acid esters, and combinations thereof. An example of a sorbitanfatty acid ester useful in the present invention is SPAN 60, which issorbitan monostearate. SPAN 60 is available from ICI Americas, Inc.,Wilmington, Del. An example of a polyoxyethylene sorbitan fatty acidester useful in the present invention is TWEEN 60, which ispolyoxyethylene(20) sorbitan monostearate. TWEEN 60 is available fromICI Americas, Inc., Wilmington, Del. The amount of surfactant in theemulsion ranges from about 0.5 to about 5 wt %, based on the totalweight of the emulsion.

More than one surfactant may be employed in the emulsion. A preferredcombination of surfactants is a sorbitan monostearate and apolyoxyethylene sorbitan monostearate, wherein the combination ofsurfactants is present in an amount ranging from about 0.5 to about 5wt. %.

In one embodiment, starch used in the emulsions of the present inventionis complexed starch. The starch may be complexed in situ, duringmanufacture of the emulsion, or the starch may be pre-complexed prior tobeing added to the emulsion. Starch is preferably complexed by mixingthe starch with a complexing agent such as a borate compound or amolybdenum compound. Compounds useful as complexing agents includeammonium biborate, ammonium pentaborate, sodium tetraborate (borax),potassium pentaborate, potassium tetraborate, lithium tetraborate, andmagnesium borate compounds; ammonium dimolybdate, ammoniumheptamolybdate, barium molybdate, calcium molybdate, lithium molybdate,magnesium molybdate, sodium molybdate, and potassium molybdate;molybdenum disulfide, and other molybdenum compounds, and the like. Thestarch useful in malting the complexed starch of the present inventionincludes, but is not limited to, corn, rice, wheat, potato, sago andother starches. The ratio of complexing agent (a borate compound, or amolybdenum compound) to starch is important to the functionality of thecomplexed starch in the emulsions. It has been found that the ratio maybe as low as 1:20, of complexing agent (a borate compound, or amolybdenum compound) to starch on a weight per weight basis. The ratiomay be as high as 1:3.5, however it has been found that at this ratio,and higher ratios, a greater amount of complexed starch is needed in theemulsion to maintain the balance of desired properties in the gypsummixture and final gypsum product. These desired properties includefluidity, foamability, and water-resistance.

Incorporating alkyl phenols into the emulsions has been found importantto achieving low water absorption in the final gypsum wood fiberproduct. As used herein, “alkyl phenols” refer to phenolic compoundshaving a long chain alkyl group. The long chain alkyl group may bestraight or branched. The long chain alkyl group may be C₂₄-C₃₄ (from 24to 34 carbon chain length). Such alkyl phenols include long chain,C₂₄-C₃₄ (from 24 to 34 carbon chain length) polymerizedmethylene-coupled alkyl phenol, phenate salts, calcium phenates, longbranched chain calcium alkyl phenols, long straight chain calcium alkylphenols and complex polymers of maleic acid with and without an aminegroup substitution. One example of an alkyl phenol useful in thecompositions of the present invention is described below. IdentificationNo. Description Source 319H C₂₄-C₃₄ polymerized methylene- LubrizolChem. Corp. coupled alkyl phenol Wycliffe, Ohio

The amount of alkyl phenol present in the emulsion ranges from about 0.5to about 10 wt %, based on the total weight of the emulsion.

Starch compounds such as acid-modified, hydroxyethylated, oxidized,and/or cationic may also be added to the emulsion. The amount of starchranges from about 0.1 to about 2 wt. %, based on the total weight of theemulsion.

Bactericides/fungicides can be included in the present invention. Anexample of a bactericide fungicide is METASOL D3TA, which is3,5-dimethyl-tetrahydro-1,3,5,2H-thiadiazine-2-thione. METASOL D3TA maybe obtained from Ondo-Nalco, Houston, Tex.

A salt of polynaphthalenesulfonic acid is required by the presentinvention. An example of a polynaphthalenesulfonic acid is DISAL GPS.The polynaphthalenesulfonic acid and an alkali metal hydroxide arereacted to give a salt of the polynaphthalenesulfonic acid. DISAL GPSmay be obtained from Handy Chemical, Montreal, Quebec, Canada.

Wax Emulsions including Polynaphthalenesulfonic Acid

Table 2 below provides examples of emulsions made according to theembodiments of the present invention. Weights are expressed in terms ofgrams. TABLE 2 Components Example 1 Example 2 Example 3 Honeywell 3816D33.00 37.90 37.90 Polyphenol 319H 0.50 5.00 5.00 Montan Wax 1.50 5.005.00 SPAN 60 0.15 0.30 0.30 TWEEN 60 0.85 1.70 1.70 45.5% KOH 0.10 0.10DISAL GPS 1.00 Starch 1.63 Borax 0.38 Water 61.25 50.00 49.00

Alternatively, the emulsion of the present invention can include auseful complexing agent such as a borate compound or a molybdenumcompound. The emulsion of the present invention can include a starch.The emulsion of the present invention can include a complexed starchthat is a complex of a starch and a complexing agent selected from aborate compound, a molybdenum compound, and the like.

There has been disclosed in accordance with the principles of thepresent invention an emulsion and gypsum wood fiber product made usingsuch an emulsion. The emulsion is useful in imparting water-resistanceto the gypsum wood fiber product. While certain embodiments and bestmode of the present invention are described herein, these embodimentsare merely illustrative. It will be apparent to those skilled in the artthat modifications may be made therein without departing from the spiritof the invention and the scope of the appended claims.

1. An emulsion comprising: at least one wax; an alkyl phenol; at leastone surfactant; polynaphthalenesulfonic acid; an alkali metal hydroxide;and water.
 2. The emulsion of claim 1 wherein the alkali metal hydroxideis selected from the group consisting of sodium hydroxide and potassiumhydroxide.
 3. The emulsion of claim 1 wherein the alkyl phenol is aC₂₄-C₃₆ polymerized methylene coupled alkyl phenol.
 4. The emulsion ofclaim 3 wherein the C₂₄-C₃₆ polymerized methylene coupled alkyl phenolis present in an amount from about 0.5 to about 10 wt. %, based on thetotal weight of the emulsion.
 5. The emulsion of claim 1 wherein thesurfactant is selected from the group consisting of a sorbitan ester, apolyoxyethylene sorbitan ester, and combinations thereof.
 6. Theemulsion of claim 5 wherein the sorbitan ester is sorbitan monostearate.7. The emulsion of claim 6 wherein the sorbitan monostearate is presentin an amount from about 0.5 to about 5 wt. %, based on the total weightof the emulsion.
 8. The emulsion of claim 5 wherein the polyoxyethylenesorbitan ester is polyoxyethylene sorbitan monostearate.
 9. The emulsionof claim 8 wherein the polyoxyethylene sorbitan monostearate is presentin an amount from about 0.5 to about 5 wt. %, based on the total weightof the emulsion.
 10. The emulsion of claim 1 wherein the surfactant is acombination of sorbitan monostearate and polyoxyethylene sorbitanmonostearate.
 11. The emulsion of claim 10 wherein the combination ofsorbitan monostearate and polyoxyethylene sorbitan monostearate ispresent in an amount from about 0.5 to about 5 wt. %, based on the totalweight of the emulsion.
 12. The emulsion of claim 1 wherein a first waxhas a melting point of at least 120° F., and a second wax is asaponifiable wax.
 13. The emulsion of claim 12 wherein the first wax ispresent in an amount from about 30 to about 45 wt. % and the second waxis present in an amount from about 3 to about 5 wt. %, based on thetotal weight of the emulsion.
 14. The emulsion of claim 1 wherein thepolynaphthalenesulfonic acid is present in an amount from about 0.25 toabout 5 wt. %, based on the total weight of the emulsion.
 15. Theemulsion of claim 1 further comprising a starch.
 16. The emulsion ofclaim 15 wherein the starch is a complexed starch comprising a starchand a complexing agent selected from the group consisting of a boratecompound and a molybdenum compound.
 17. The emulsion of claim 16 whereinthe starch is selected from the group consisting of unmodified starch,acid-modified starch, hydroxyethylated starch, oxidized starch, andcationic starch.
 18. The emulsion of claim 17 wherein the starch isacid-modified starch.
 19. The emulsion of claim 16 wherein the ratio ofthe complexing agent to the starch on a weight per weight basis is fromabout 1:4 to about 1:20.
 20. A method for making an emulsion, comprisingthe steps of: (a) heating to a temperature ranging from about 185° F. toabout 210° F. a mixture containing at least one wax, an alkyl phenol,and at least one surfactant selected from the group consisting of asorbitan ester and a polyoxyethylene sorbitan ester, producing a waxphase mixture; (b) heating to a temperature ranging from about 185° F.to about 210° F. a mixture containing polynaphthalenesulfonic acid, analkali metal hydroxide, and water, producing a water phase mixture; (c)adding the water phase mixture to the wax phase mixture to provide amixture; (d) homogenizing the mixture of step (c) at a pressure fromabout 2000 psig. to about 4000 psig.; and (e) cooling the homogenizedmixture at a rate effective to control the stability and viscosity ofthe homogenized mixture.
 21. The method of claim 20 wherein the alkalimetal hydroxide is selected from the group consisting of sodiumhydroxide and potassium hydroxide.
 22. The method of claim 20 whereinthe alkyl phenol is a C₂₄-C₃₆ polymerized methylene coupled alkylphenol.
 23. The method of claim 20 wherein the surfactant is acombination of sorbitan monostearate and polyoxyethylene sorbitanmonostearate.
 24. The method of claim 20 wherein a first wax has amelting point of at least 120° F., and a second wax is a saponifiablewax.
 25. The method of claim 20 wherein a complexed starch, comprising astarch and a complexing agent selected from the group consisting of aborate compound and a molybdenum compound, is added to the water phasemixture.
 26. An emulsion comprising: a first wax having a melting pointof at least 120° F. in an amount of about 30 wt. % to about 45 wt. % byweight, based on the total weight of the emulsion; a saponifiable wax inan amount from about 3 to about 5 wt. %, based on the total weight ofthe emulsion; a combination of surfactants in an amount from about ofabout 0.5 to about 5 wt. %, based on the total weight of the emulsion;an alkyl phenol in an amount from about 0.5 to about 10 wt. %, based onthe total weight of the emulsion; a polynaphthalenesulfonic acid in anamount from about 0.25% to about 5 wt. %, based on the total weight ofthe emulsion; water in an amount from about 45 to about 65 wt. %, basedon the total weight of the emulsion; and an alkali metal hydroxide in anamount from about 0.5% to about 3 wt. %, based on the total weight ofthe emulsion.
 27. The emulsion of claim 26 further comprising acomplexed starch, the complexed starch comprising a starch and acomplexing agent selected from the group consisting of a borate compoundand a molybdenum compound.
 28. A method for making a gypsum wood fiberarticle, comprising the steps of: (a) mixing a slurry containing fromabout 5 wt. % to about 50 wt. % of a wood fiber, from about 5 wt. % toabout 50 wt. % of gypsum, from about 1 wt. % to about 3 wt. % of theemulsion of claim 27, based on the total weight of the slurry and water;(b) distributing the slurry onto a vacuum wire for formation of a mat;(c) partially drying the mat of step (b); (d) compressing the mat ofstep (c) through a series of vacuum belt rolls; and (e) drying thecompressed mat of step (d) in an oven.
 29. The method of claim 28wherein the wax emulsion comprises: a first wax having a melting pointof at least 120° F. in an amount of about 30 to about 45 wt. %, based onthe total weight of the emulsion; a saponifiable wax in an amount fromabout 3 to about 5 wt. %, based on the total weight of the emulsion; acombination of surfactants in an amount from about 0.5 to about 5 wt. %,based on the total weight of the emulsion; an alkyl phenol in an amountfrom about of about 5% to about 10% wt. %, based on the total weight ofthe emulsion; a polynaphthalenesulfonic acid in an amount from about0.25% to about 5% wt. %, based on the total weight of the emulsion;water in an amount from about 45 to about 65 wt. %, based on the totalweight of the emulsion; and an alkali metal hydroxide in an amount fromabout 0.5% to about 3 wt. %, based on the total weight of the emulsion.30. The method of claim 29 wherein the wax emulsion further comprises acomplexed starch, the complexed starch comprising a starch and acomplexing agent selected from the group consisting of a borate compoundand a molybdenum compound.
 31. A wallboard made by the method of claim28.
 32. A wallboard made by the method of claim
 29. 33. A wallboard madeby the method of claim
 30. 34. A sheathing made by the method of claim28.
 35. A sheathing made by the method of claim
 29. 36. A sheathing madeby the method of claim
 30. 37. A gypsum wood fiber article, comprising:(a) a wood fiber; (b) gypsum; and (c) a wax emulsion.
 38. The gypsumwood fiber article of claim 37, wherein the wax emulsion comprises: afirst wax having a melting point of at least 120° F. in an amount ofabout 30% to about 45% by weight, based on the total weight of theemulsion; a saponifiable wax in an amount from about 3% to about 5% byweight, based on the total weight of the emulsion; a combination ofsurfactants in an amount from about of about 0.5% to about 5% by weight,based on the total weight of the emulsion; an alkyl phenol in an amountfrom about of about 0.5% to about 10% by weight, based on the totalweight of the emulsion; a polynaphthalenesulfonic acid in an amount fromabout 0.25% to about 5% by weight, based on the total weight of theemulsion; water in an amount from about 45% to about 65% by weight,based on the total weight of the emulsion; and an alkali metal hydroxidein an amount from about 0.5% to about 3% by weight, based on the totalweight of the emulsion.
 39. The gypsum wood fiber article of claim 38,wherein the wax emulsion further comprises a starch.
 40. The gypsum woodfiber article of claim 38, wherein the wax emulsion further comprises acomplexed starch, the complexed starch comprising a starch and acomplexing agent selected from the group consisting of a borate compoundand a molybdenum compound.
 41. The gypsum wood fiber article of claim37, wherein the wood fiber is selected from hardwood and softwoodsources, and mixtures thereof.
 42. The gypsum wood fiber article ofclaim 38, wherein the wood fiber is selected from hardwood and softwoodsources, and mixtures thereof.
 43. A gypsum wood fiber article,comprising: (a) a wood fiber; (b) gypsum; and (c) a wax emulsion, thewax emulsion a complexed starch, the complexed starch comprising astarch and a complexing agent selected from the group consisting of aborate compound and a molybdenum compound.
 44. The gypsum wood fiberarticle of claim 43, wherein the wood fiber is selected from hardwoodand softwood sources, and mixtures thereof.